Drive circuit for counting tubes



July 29, 1958 J. E. ADAMS DRIVE CIRCUIT FOR COUNTING TUBES Filed Aug.24, 1956 Fig. I

OUTPUT g \T 1 J r29 2 3O gas INVENTOR. JOHN E. ADAMS zazjuu ATTORNEYSUnited States Patent 2,845,578 DRIVE CIRCUIT FOR COUNTING TUBES John E.Adams, Newtonville, Mass,

Electric Products Inc, Salem, Massachusetts Application August 24, 1956,serial No. seam 11 Claims. (Cl. 31584.6)

asslgnor to Sylvania Mass., a corporation of veloped was the ringcircuit. The circuit included a group of electron tubes arranged in aring and operable one at a time. Each tube, as it conducted current,designated a digit or other unit of data. Recently, many types ofcounting tubes have become available which incorporate several countingstages within one tube envelope. These tubes are generally, although notnecessarily, constructed to provide for a count of ten and may becascaded to provide a decimal counting system to any order of magnitudedesired. The count at any instant can be read out from the activatedstage in each tube.

One category of these counting tubes is composed of the so-called gasfilled glow transfer counting tubes of which there are many diflTeringtypes. All of the types, however, are multiple element tubes wherein aglow on one of the elements indicates visually and electrically a unitof data. Each impulse reaching the tube is counted and indicated by thechange of the position of the glow from one element to another elementin a predetermined pattern.

This invention contemplates the use of a glow transfer tube employing acentral anode and three sets or groups of cathodic electrodes. One setof the cathodic electrodes serves as the main or count indicatingcathodes, and the other two sets are the so-called guide electrodes orguides. The transfer action of these tubes requires a driving circuit toconvert input pulses into signals which are capable of switching theposition of the glow from a main cathode to intervening guide electrodesand then on to the next main cathode in proper sequence.

The envelope of the tube is gas filled and has a discshaped anodelocated at its center. Arranged in an annular row about the anode arethirty (for a decimal counting system) equally spaced rod-like cathodicelectrodes. Every third cathodic electrode is designated as a main orcount indicating cathode. These main cathodes may be electricallyconnected together but generally one or more are arranged to provideindependent electrical outputs. The remaining cathodes are divided intotwo groups, all of the members of each group being connected together toform two sets of guide or transfer electrodes. Switching of the glowfrom one main cathode to the next main cathode to effect a count isaccomplished in the following manner. The potential of one set of guideelectrodes is lowered to the point where the glow will leave itsposition on the main cathode and transfer to the nearest guide electrodeof that set. The potential of the second set of guide electrodes is thenlowered while the potential of the first set is allowed to return to itsnormal value. When the potential on the second set is sufiiciently lowerthan that on the first set, the glow e will transfer from its positionon a guide electrode of the first set to the adjacent guide electrode ofthe second ICE set. The potential of the second set of guide electrodesis then allowed to return to its normal value. The normal potentials onthe second set of guide electrodes and on the main cathodes are suchthat the glow will then move from the second electrode to the adjacentmain cathode. Thus, the glow is moved in a predetermined direction fromone main cathode via two guide electrodes to the next main cathode toeffect a count.

The result described above is achieved by means of a particular drivingcircuit for the tube. The driving circuit must provide appropriatesignals of proper potential, wave shape, and time relationship for eachinput pulse received. A simple circuit in which an input pulse isapplied directly to one set of guide electrodes and through anappropriate delay circuit to the second set of electrodes may worksatisfactorily in some applications. It has been the practice, though,to provide some amplification for the input pulses to improveperformance.

At the other end of the scale, some very complicated circuits have beendesigned to produce in response to the input pulses being counted,signals to the guide electrodes which are nearly ideal in wave shape andtiming. In fact, it is unnecessary that wave shapes be idealized, but itis highly desirable that reliability of counting be maintained and thatthe drive circuit be capable of opera.- tion at frequency rates at leastas high as those at which the counting tube itself can operate. Neitherthe circuit of the simple type with its inherent unreliability nor thecomplicated circuit with its elaborate and expensive components hasadequately filled these needs.

it is therefore an object of my invention to provide an electrondischarge impulse counting circuit capable of operating at high inputfrequencies.

It is another object of this invention to provide a highly reliableelectron discharge impulse counting circuit.

It is a further object of this invention to provide a driving circuitfor delivering a set of output pulses or switching signals in responseto and in timed relationship to each input pulse.

In general, the present invention consists in a drive circuit and glowtransfer counting tube operable in response to input pulses or signalsas modified by the drive circuit. The drive circuit develops theswitching signals for application to the guide or transfer electrodes byutilization of the leading edge, the crest, and the trailing edge of theinput pulse. The leading edge is utilized to excite a first tube whichtransfers the ionization path in the' counting tube from a main cathodeto a guide electrode. The leading'edge also excites a second tube andthe crest temporarily maintains conduction in that second tube. Theoutput of the second tube is inverted with respect to the input pulse,and the trailing edge of the input pulse, as so inverted, in combinationwith the input pulse, causes excitation of a third tube which transfersthe ionization path to a second guide electrode in the counting tube.Cessation of conduction of current in the third tube completes a cycleof transfer of the ionization path in the counting tube by switching itto the next main cathode. For a better understanding of the presentinvention, together with other objects, features and advantages,reference should be made to the following detailed description of apreferred embodiment and the accompanying drawing the single figure ofwhich is a schematic diagram of one embodiment of the circuit and tubeof the present invention.

The gas filled glow transfer counting tube 10 shown in the drawingincludes a disc-shaped anode 11 surrounded by slim rod-like cathodicelements arranged in an annular row. Each third cathodic electrode 12,12a, 12b, 12c and 12a is designated as a main or count-indicatingcathode. In the drawing, there is illustrated a counting tube havingonly five rather than the ten stages previously U noted as beingpreferred for easy adaptation to decimal counting. This has been done toavoid unduly complicating the drawing and to simplif the explanation ofthe invention. The ten stage device would, of course, operate in thesame manner as that shown and described.

Adjacent each main cathode are two guide electrodes. For example,adjacent main cathode 12 in a clockwise direction is a guide electrode13, adjacent main cathode 12a in a clockwise direction is a guideelectrode 135. Similarly, the guide electrodes 13b, 13c and 13d areadjacent in a clockwise direction main cathodes 12b, 12:- and 12drespectively. Going in a counter-clockwise direction, guide electrodes14, 14a, 14b, 14c and 14d lie adjacent main cathodes 12, 12a, 12b, 12cand 12:! respectively. Guide electrodes 13, 13a, 13b, 13c and 130! areall electrically connected together through the line shown as theinnermost wiring ring in the drawing. Guide electrodes 14, 14a, 14b, 14cand 14d are similarly connected together through the middle wiring ring.Main cathodes 12, 12b, 12c and 12d are also connected together throughthe outermost wiring ring, cathode 12a being independent of directconnection to the ring for purposes explained below.

The anode 11 is connected through a resistor 15 to a point of highpositive potential at the top of a voltage divider 16. The main cathode12a is selected as the output cathode and is connected through aresistor 17 to another and lower point of positive potential 18 onvoltage divider 16. An output terminal 19 is connected to the maincathode 12a. Similar connections may be provided for other main cathodesin those instances where it is desired to obtain additional outputs. Inthe embodiment shown, however, the four remaining main cathodes are allconnected directly to the point of positive potential 18. A normallyopen reset switch 37 is connected between the main cathode 12a andground to enable the glow to be removed from any other cathode and to beestablished on main cathode 12a as is more fully explained below.

A duo-triode 22 composed of a first triode section 22a and a secondtriode section 22b is shown. Separate triode tubes could, of course, beused instead of the duotriode 22, since there is no interaction betweenthe sections. The first set of guide electrodes 13, 13a 13!), etc. isconnected to the anode 20 of triode 22a. The second set of guideelectrodes 14, 14a, 14b, etc. is connected to the anode 21 of triode22b. The cathodes 23 and 2- of the duo-triode are connected together andto a point 39 of still lower positive potential on the voltage divider16 than point 18. The control grid 25 of triode 22a is connected to thepositive input terminal 26. The control grid 27 of triode 22b isconnected through a resistor 28 to the input terminal 26 and through acapacitor 29 to the anode 30 of the triode 31. The anode 30 is alsoconnected through a resistor 32 to the point of positive potential 18 onvoltage divider 16. The cathode 33 of triode 31 is connected to thepoint of low positive potential 39, on voltage divider 16 and thecontrol grid 34 is connected to the input terminal 26. An input gridresistor 35 is connected between input terminal 26 and the groundedinput terminal 36.

In a typical circuit of the type described and shown, the tubes employedwere a Sylvania Type 6802 as the glow transfer tube 10; a Sylvania Type616 as the duo triode 22 and a Sylvania Type 6C4 as the triode 31. Thevoltage divider 16 provided 500 volts at its maximum tap from whichpoint it was connected through the plate resistor 15 to the anode 11.The resistor 15 had a value of 430,000 ohms. The resistor 17 connectedto the output terminal 19 had a value of 24,000 ohms and the voltage atits point 18 of connenction to divider 16 was 100 volts. The plateresistor 32 had a value of 100,000 ohms and the differentiating circuitelements condenser 29 and resistor 28 had values of 10 micro-microfaradsand 360,000 ohms respectively. The three cathodes of the triode 31 and avider 16.

Y 4. due triode 22 were connected to the point 39 of the divider 16where the voltage was 7 volts. The input re sistor 35 had a value of150,000 ohms.

Considering the typical circuit for the moment with the cited voltagesapplied, a glow will take place immediately at one of the main cathodes.The particular main cathode which assumes the glow will be determined bysome asymmetrical condition existing in the tubes or circuit whichcauses a lower potential to appear at one main cathode. A main cathodewill assume the glow rather than a guide electrode because all maincathodes are lower in voltage than the guide electrodes. In the typicalcircuit being considered presently the main cathodes are at voltsderived from point 18 of the di- It will be seen that the guideelectrodes are at a potential greater than 100 volts. Althoughduo-triode 22 is cut-01f by reason of the cathodes being con nected to+7 volts at point 39 of divider 16 with the grids at ground potential, acertain minimum plate current is actually flowing in the two sections ofduo-triode 22. This minimum current is of a value (c. g., a fewmicroamperes) determined by the requirement for electrons to neutralizethe stray gaseous ions present in the annular zone between the anode andcathode array of the glow discharge tube at points other than the zoneof the existing visible glow. At this value of plate current, thevoltage drop across the sections of duo-triode 22 is considerable. Thevoltage at the anodes 20 and 21 which is in fact the voltage on theguide electrodes is therefore also quite high, considerably in excess ofthe 100 volts on the main cathodes.

To initiate counting at a desired main cathode, a manually operablereset system is provided. In the circuit of Fig. 1, temporarily closingthe normally open switch 37 grounds main cathode 12a placing it wellbelow the potential of the other tube elements, and therefore cathode12a assumes the glow. On reopening the switch to return the circuit to anormally biased condition the glow will remain on main cathode sincenone of the counting tube elements is at a potential low enough to causeswitching or transfer of the glow.

The action taking place in the circuit elements by which the glow istransferred from one main cathode to the next is described below.

Assuming the glow is taking place at main cathode 12a, switch 37 havingbeen momentarily closed to ground cathode 12a, a circuit is completedfrom the topof voltage divider 16 through resistor 15, to anode 11, to,cathode 12a, and through resistor 17 to a relatively low point 18 onvoltage divider 16. Both sections 22a and 22b of duo-triode 22 remainjust below cut-off in the absence of a signal on their control gridsbecause their cathodes 23 and 24 are electrically tied to the point 39of positive potential on divider 16. The anode 30 of triode 31 iselectrically connected to point 18 of positive potential on divider 16,and its cathode is also returned to point 39 of low positive potential.I-Ience, triode 31 also remains non-conducting in the absence of asignal.

With the application of a positive input pulse across input terminals 26and 36, the switching action begins. A sinusoidal pulse will beconsidered although pulses of other shapes can be counted by means ofthis invention with minor modifications.

The applied input pulse appears directly at grid 34 of triode 31 and atgrid 25 of triode section 2211. Triodes 31 and 22a immediately begin toconduct current more heavily. The increasing current through triodesection 22a causes a decreasing voltage to appear at anode 20 of thatsection. Anode 2 0 is directly connected to the set of guide electrodeswhich includes electrode 13:: and the dropping voltage accordinglyappears at 13a. The actual curve of potential drop at electrode 13a isan :tmpli fied inverted replica of the input signal. As the potential onguide electrode 13a drops sufficiently below that of cathode 12am glowdischarge from anode 11 transfers from main cathode 12a to guideelectrode 13a.

At the same time, the voltage on the set of guide electrodes whichincludes electrode 14b must be considered. The voltage at that set ofelectrodes goes through the following changes. Triode 31, as mentionedabove, be-

gins to conduct more heavily when the input pulse is applied to its grid34. The increased current through triode 31 develops a voltage acrossresistor 32 such that the voltage at the anode 30 appears approximatelyas the inverse of the input pulse.

The inverted voltage so obtained is differentiated by the circuitcomposed of condenser 29 and resistor 28. Therefore, the leading edgeand crest of the applied input pulse as inverted and differentiatedappear at the grid 27 of triode section 2211 as a negative voltage anddo not cause triode section 22b to conduct current.

The trailing edge of the input pulse, however, causes the current beingpassed by triode 31 to decrease. Correspondingly, the voltage developedacross resistor 32 decreases and anode 3t rises in voltage. The risingvoltage at anode 30 is coupled to the grid 27 of triode section 22bcausing that section to begin to conduct current. As the conductionincreases, the voltage at anode 21 and, of course, at the transferelectrodes including 14b drops, transferring the glow discharge to thatelectrode. During the occurrence of the trailing edge of the input pulsethe voltage on the electrodes including 13a is rising as conductionthrough triode section 22a decreases, permitting the transfer of theglow from guide electrode 13a to 14b to occur.

The switching action is completed prior to the termination of the inputpulse. With no further signal on the grids of triode 31 or duo-triodesections 22a and 22b, the voltage on anodes 20 and 21, and therefore onboth groups of guide electrodes return to their normal bias potentialscausing the glow discharge to shift to main cathode 1212.

Another explanation of the switching sequence is had by considering thevoltage appearing at grid 27 of triode section 22b to be the result ofcombined eifects. As the glow discharge shifts to guide electrode 13a,during the occurrence of the leading edge of the input pulse, the anodevoltage at anode 30 of triode 31 is decreasing from its prior value to avalue determined by the voltage at point 18 on the divider 16 less thevoltage developed across resistor 32. Condenser 29, having previouslybecome charged to the full value of voltage at point 18 during thequiescent period between pulses, tends to discharge to reach anequilibrium point with the voltage now present at its terminals. This,of course, causes the voltage at grid 27, the junction of condenser 29and resistor 28, to drop, maintaining triode section 22b cut off.

However, as the input pulse crests and the voltage at anode 30 begins togo in a positive direction the rate of discharge of condenser 29declines. also present on grid 27 directly by way of resistor 28, and asthe rate of discharge of condenser 29 approaches zero, the directlyapplied input pulse is temporarily the only voltage present at grid 27and causes the triode section 22b to conduct, lowering the voltage atanode 21 and guide electrode 14!) to begin transfer of the glowdischarge to that guide electrode. The trailing edge of the pulse isadded to by the positive going voltage at anode 30 which causes acharging current to flow into the condenser making the junction ofresistor 28, condenser 29 and grid 27 more positive than would be thecase if the input pulse alone were effective on grid 27. This causestriode 22b to continue conduction until after triode 22a no longerconducts enough to retain the discharge on guide electrode 13a, andthereby the transfer of the discharge to guide electrode 14b iscompleted. As the condenser 29 becomes more fully charged, its chargingrate decreases and reaches zero when the voltage on the The input pulseis.

condenser reutrns to the value it had prior to the occurrence of theinput pulse. This return closely follows termination of the trailingedge of the input pulse. With the return of the circuit to the steadystate condition, the glow discharge transfers to the next main cathode.

With each successive input pulse, the sequence of actions is repeated,the glow discharge going in a clockwise direction from one main cathodeto the next via the intrevening guide electrodes. At each revolution ofthe glow discharge away from main cathode 12a, an output signal resultsand maybe taken from point 19. This occurs because of the presence ofresistor 17 between main cathode 12a and the other main cathodes. Whenthe current of the glow discharge is flowing from cathode 12a throughresistor 17 a voltage is developed across that resistor and is, ofcourse, present between output terminal 19 and ground. When the glowdischarge transfers to guide electrode 13a, the current through resistor17 ceases and the voltage at output terminal 19 drops to the value ofthe voltage at point 18 on the divider. This is the same voltage whichis present at all other main cathodes.

Conversely, when the glow discharge transfers to cathode 12a, thevoltage across resistor 17 is initiated. In effect, then, an outputpulse is present at terminal 19. Its durationis the length of time thatthe 'glow discharge is present at cathode 12a. Its frequency isone-fifth that of the input signal inasmuch as it takes five inputpulses to cause the glow discharge to travel completely around tube 10.It is obvious that a cascaded arrangement of decade counter tubes can beused to count any finite quantity of units capable of representation bypulses.

Although a specific embodiment of the present invention has beendescribed and illustrated, numerous modifications within the purview ofthe present invention will suggest themselves to those skilled in theart. For example, resistor 28 might be returned to ground rather thantothe input voltage. This, however, would render the circuit more criticalas to input wave shape, pulse crest value' and frequency. Also,transistors might well replace the vacuum tubes in the drive circuitwithout departure from the concepts of the present invention.

Still another modification which suggests itself is the use of two ormore circuits of the type illustrated with a single glow transfer tube.Thus, by the inclusion of another exciting circuit for the driving tube22, for operation in reverse order, subtraction as well as addition canbe carried out. Because of the foregoing, as well as other,modifications which immediately suggest themselves to those skilled inthe art, the present invention should be limited only by the spirit andscope of the appended claims.

What is claimed is:

1. A drive circuit for a glow transfer tube for counting input pulses,said tube having an anode, a plurality of cathodes, a first plurality ofguide electrodes, and a second plurality of guide electrodes, saidcathodes and said guide electrodes being so disposed that adjacent eachcathode in a clockwise direction there lies one of said first pluralityof guide electrodes and adjacent each cathode in a counter-clockwisedirection there lies one of said second plurality of guide electrodes,comprising means for establishing a glow discharge between said anodeand one of said plurality of cathodes, means for lowering the potentialof said first set of guide electrodes below that of said cathodesimmediately in response to each of said input pulses to transfer saidglow discharge from said one of said plurality of cathodes to the one ofsaid first set of guide electrodes adjacent thereto, means for invertingand differentiating each of said input pulses, means for combining eachof said input pulses with an inverted and diflerentiated pulse toprovide a delayed pulse, means for lowering the potential of said secondset of guide electrodes below that of said first set of guide electrodesin response to said delayed pulse to transfer said glow discharge fromsaid one of said first plurality of guide electrodes to the one of saidsecond plurality of guide electrodes adjacent thereto, said glowdischarge being transferred to another of said plurality of cathodesadjacent said one of said second plurality of guide elec trodes uponincrease of potential on said second plurality of guide electrodes abovethat of said plurality of cathodes on cessation of said delayed pulse.

2. Impulse counting apparatus comprising a glow transfer tube having aplurality of cathodes, a first plurality of guide electrodes, and asecond plurality of guide electrodes, means for establishing a glowdischarge at one of said cathodes, means for transferring said glowdischarge to one of said first plurality of guide electrodes immediatelyupon occurrence of one of said impulses, means for inverting anddifferentiating each of said impulses, means for combining each of saidimpulses with an inverted and differentiated impulse to provide adelayed pulse, and means for transferring said glow discharge to one ofsaid second plurality of guide electrodes in response to said delayedpulse.

3. A drive circuit for a glow transfer tube comprising a first vacuumtube for providing a first negative voltage pulse in immediate responseto a positive input pulse, a second vacuum tube for providing a secondnegative voltage pulse in immediate response to the positive inputpulse, a differentiating circuit connected to said second vacuum tubefor differentiating said second negative voltage pulse, a third vacuumtube, means for combining the positive input pulse with thedifferentiated second negative voltage pulse, means for applying theoutput of said last-mentioned means to said third vacuum tube to producea third negative voltage pulse delayed in time relative to said firstnegative voltage pulse and means connecting said first and said thirdvacuum tubes to said glow transfer tube to couple said first and saidthird negative voltage pulses thereto.

4. A drive circuit for providing sequential negative voltage pulses to aglow transfer counting tube in response to positive input pulsescomprising means for converting said positive input pulses to negativeswitching pulses immediately upon occurrence thereof, means forinverting and differentiating each said positive input pulse, means forcombining each said positive input pulse with an inverted anddifferentiated pulse, and means for converting the output pulses of saidcombining means into second negative switching pulses, and means forapplying said first and said second negative switching pulses to saidglow transfer counting tube.

5. A drive circuit for providing sequential negative voltage pulses to aglow transfer counting tube in response to positive input pulsescomprising means for providing a first negative voltage pulse to saidcounting tube in response to the occurrence of a postive input pulse,said first negative voltage pulse being substantially an invertedreplica of said input pulse and originating in timed relationship withthe leading edge of said input pulse, and means for providing a secondnegative voltage ulse to said counting tube in response to the trailingedge of said input pulse.

6. A drive circuit for a glow transfer tube for counting input pulsescomprising a first means for generating a first switching pulse inresponse to the leading edge of each said input pulse, a second meansfor generating a second switching pulse in response to the trailing edgeof each said input pulse, said second means comprising means forinverting each said input pulse and means for differentiating eachinverted input pulse, and means for coupling said first and secondswitching pulses to said glow transfer tube.

7. A drive circuit for a glow transfer tube for counting positive inputpulses comprising a first vacuum tube connected in series with a firstset of glow transfer electrodes in said glow transfer tube, a secondvacuum tube connected in series with a second set of glow transferelectrodes in said glow transfer tube, means for applying said inputpulses directly to said first tube to increase conduction therein, saidfirst set of glow transfer electrodes being immediately lowered inpotential by the increased conduction in said first vacuum tube, meansfor inverting and differentiating said input pulses, and means forapplying said input pulses and said inverted and differentiated pulsesto said second vacuum tube to increase conduction therein and thereby tolower the potential of said second set of glow transfer electrodes.

8. A drive circuit for a glow transfer tube for counting positive inputpulses comprising a first vacuum tube having at least an anode, acathode and a control grid, the anode of said first vacuum tube beingconnected to a first set of guide electrodes in said glow transfer tube,a second vacuum tube having an anode, a cathode and a control grid, theanode of said second vacuum tube being connected to a second set ofguide electrodes in said glow transfer tube, the cathodes of said vacuumtubes being connected together and to a source of operating potential,means for applying said input pulses directly to the control grid ofsaid first vacuum tube, means for inverting and differentiating saidinput pulses and means for applying said input pulses in combinationwith said inverted and differentiated pulses to the control grid of saidsecond vacuum tube.

9. A drive circuit for a glow transfer tube for counting positive inputpulses comprising a first vacuum tube having at least an anode, acathode and a control grid, the anode of said first vacuum tube beingconnected to a first set of guide electrodes in said glow transfer tube,a second vacuum tube having an anode, a cathode and a control grid, theanode of said second vacuum tube being connected to a second set ofguide electrodes in said glow transfer tube, the cathodes of said vacuumtubes being connected, at third vacuum tube having at least an anode, acathode and a control grid, a source of operating po tential beingconnected between the anode and the cathode of said third vacuum tube,means for applying said positive input pulses to the control grids ofsaid first and said third vacuum tubes, inverted replicas of said inputpulses appearing at the anodes of said first and third vacuum tubes, andat said first set of guide electrodes in said glow transfer tube, adifferentiating circuit connected to the anode of said third vacuumtube, and means for coupling input pulses directly and the output pulsesof said differentiating circuit tothe control grid of said second vacuumtube, the anode of said second vacuum tube and said second set of guideelectrodes being thus lowered in potentialafter the lowering inpotential of said first set of guide electrodes.

10. Pulse counting apparatus comprising a glow transfer tube having aplurality of circularly arranged cathodes, an anode, a first set ofguide electrodes each guide electrode of said first set being adjacentin a clockwise direction one of said cathodes, and a second set of guideelectrodes, each guide electrode of said second set being adjacent in acounterclockwise direction one of said cathodes, a voltage divider,means connecting said glow tube anode to a first point of high voltageon said divider, three vacuum tubes each having at least an anode, acathode and a control grid, said first set of guide electrodes beingconnected together and to the anode of the first of said vacuum tubes,said second set of guide electrodes also being connected together and tothe anode of the second of said vacuum tubes, said plurality of glowtube cathodes, less one, being connected together and to a second pointon said voltage divider of lower voltage than said first point, aresistor connecting said one glow tube cathode to the remainder of saidglow tube cathodes, an output terminal at the junction of said resistorand said one cathode, and a normally open momentary contact switchconnected between said junction and ground, the cathodes of said first,second and third vacuum tubes being connected together and to a thirdpoint on said voltage divider of lower voltage than said second point,the anode of said third vacut'm tube being connected to said secondpoint on said voltage divider, means for coupling said pulses to becounted to the control grids of said three vacuum tubes, a negativevoltage pulse appearing immediately on the anode of said first vacuumtube and on said first set of guide electrodes in response to each ofsaid input pulses appearing at the control grid of said first vacuumtube, a negative voltage pulse also appearing at the anode of said thirdvacuum tube, a differentiating circuit connected between the anode ofsaid third vacuum tube and the control grid of said second vacuum tube,the output of said differentiating circuit and said input pulseappearing simultaneously at the control grid of said second vacuum tube,whereby a negative voltage pulse appears on said second vacuum tubeanode and on said second set of guide electrodes subsequent to theappearance of a negative voltage pulse on said first set of guideelectrodes.

11. A drive circuit for a tube for counting input pulses comprisingthree vacuum tubes each having at least a cathode, a control grid and ananode, means for providing anode voltage to said three vacuum tubes,means for providing operating potentials to said cathodes of said threevacuum tubes, means for applying said input pulses directly to saidcontrol grids of the first and second of said vacuum tubes to initiatesubstantially immediate increased conduction in the first and second ofsaid vacuum tubes, means including a first resistance for applying saidinput pulse to the control grid of the third of said vacuum tubes, acapacitor connected between the anode of the second of said vacuum tubesand the control grid of the third of said vacuum tubes, said firstresistance and said capacitor comprising a differentiating circuit,means for applying the output of said differentiating circuit togetherwith said input pulses to the control grid of said third of said vacuumtubes to cause increased conduction of current therein after a period ofdelay and connections for providing output signals from the anodes ofsaid first and said third vacuum tubes to the tube for counting inputpulses.

References Cited in the file of this patent UNITED STATES PATENTS2,679,978 Kandiah June 1, 1954 2,700,146 Bachelet Jan. 18, 19552,714,179 Thomas et a1 July 26, 1955 2,739,266 Burnett Mar. 20, 1956

